The effect of 1,25-dihydroxyvitamin D-3 on the distribution of alkaline phosphatase activity along the chick intestinal villus

Abstract

Rachitic chicks received 2.5 nmol of 1,25-dihydroxyvitamin D-3 (1,25(OH) 2D 3) at 4, 8, 12, 24 and 48 h, respectively, before killing. A small piece of the duodenum from each chick was frozen and divided into two parts. One part was serially sectioned perpendicular to the longitudinal axis of the villi. Each section was analyzed for alkaline phosphatase and sucrase activities. The second part was sectioned parallel to the longitudinal axis of the villus to determine villar length by morphometry. The results indicate that: 1. 1. A gradient of alkaline phosphatase activity exists along the villus with maximal activity at the tip. 2. 2. 1,25(OH) 2D 3 stimulated alkaline phosphatase activity along the entire length of the villus. The responses of different regions of the villus to 1,25(OH) 2D 3 were parallel in time for the first 12–24 h indicating a lack of differential response according to cell age. By 48 h the alkaline phosphatase activity at the base of the villus had returned to control values whereas the activity at the tip of the villus remained fully stimulated. 3. 3. A significant increase in villar length was observed in the duodenal specimens from the 1,25(OH) 2D 3-treated chicks. 4. 4. Sucrase activity does not parallel alkaline phosphatase activity but is greater in the region just distal to the crypts with little activity at the villar tip or in the bottom of the crypts. 5. 5. 1,25(OH) 2D 3 had no significant effect on the amount or distribution of sucrose activity.